Method of dewaxing oils



July 28, 1936.

METHOD OF DEWAXING OILS Filed Jun e 28', 1933 1 2 Sheets-Sheet 1 w. A. EBERLE ET v ,053

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' METHOD OF DEWAXING OILS Filed June 28, 1933 2 Sheets-Sheet 2 DEWA xzzvo MACH/IVE.

WA X 00 TL E T .SubPl-V rmvk .zubvauva TANK DEM Axe on. 007257 Patented- July 28, 1936 METHOD OF DEWAXING OILS William A. Eberle and Louis H. Zepfler, Jersey v City, N. J., assignors to Standard Oil Development Company, a corporation of Delaware Application June 28, 1933, Serial No. 678,017

4 Claims. (Cl. 62-170) This invention relates to the dewaxing of oils, especially the lubricating fractions of petroleum, and is more particularly concerned with improvements in the method of chilling.

Petrolatum is ordinarily removed from petroleum oils by diluting the oil with a suitable solvent such as naphtha, raising the temperature to a point at which all wax crystals have completely dissolved, chilling the mixture to a wax-separation temperature and then centrifuging the chilled mixture. This may be done by batch operation but is more usually carried out-in a continuous manner.

In the continuous method of operation the oilsolvent mixture is passed successively through a series of chillers each of which is maintained at a lower temperature than the preceding ones.

In order to obtain the petrolatum in particles of a size suitable for rapid centrifuging, it is necessary to chill the oil-solvent mixture very gradually, say at a rate of 2 to F. per hour. Each chiller is maintained at a temperature from to 30 F. below that of the next preceding chiller.

It has been found that in passing the partially chilled mixture from one chiller to the next, a sudden drop in temperature frequently occurs at the instant the mixture is introduced into the.

next succeeding chiller. This shock chilling even though through a narrow temperature range tends to cause the petrolatum to precipitate in particles of relatively small size which do not readily separate out on centrifuging.

It is the object of the present invention to provide a method and apparatus for avoiding shock chilling on the passage of the oil-solvent mixture from one chiller to the next.

The method will be fully understood from the following description, read with reference to the accompanying drawings, of which Figure 1 is a semi-diagrammatic view in sectional elevation of a single chiller, and

Figure 2 isa semi-diagrammatic view of a series of chillers showing the lines of flow through the apparatus.

Referring to Figure 1, numeral I designates one of the chillers in a series used for continuous chilling. The mixture of oil and solvent is drawn from the next preceding. chiller by pump 2 through line 3 and flows through line 4 into and through a coil 5 immersed in the liquid in chiller I. In this coil 5 the mixture is indirectly cooled by means of the cooler liquid in chiller I. The partially cooled mixture flows out of coil 5 and if directly into the body of liquid in chiller I. If

not sufflciently cooled on one passage through coil 5, the mixture may be recycled therethrough by means of line I as many times as is found necessary to bring its temperature to within a few degrees of that of the liquid in chiller I.. Alternatively after one passage of the mixture through the coil approximately one-half of it may be discharged directly into the cooler chiller, and the other half may be mixed with warmer liquid from the preceding chiller and the mixture then 10 passed through the coil. In this way the mixture passing from a warmer chiller to a cooler chiller may be cooled gradually to the temperature of the cooler chiller.

Referring to Figure '2 numerals II], n, I2, I3,15

I4 and' I5 designate six chillers in series. Numeral I6 designates a supply tank for oil to be dewaxed. Numeral II designates a supply tank for diluent to be used. Numeral I8 designates a tank in which the oil and diluent are blended.

The mixture of oil and diluent is withdrawn from tank I8 through line I9 by means of pump 20 and forced through a coil 2| immersed in the liquid previously introduced into chiller Ill. The

mixture may be recirculated through coilv 2I as many timesas deslred,-as more clearly indicated in Figure 1. Finally the mixture is discharged through valved line 22 into chiller III. From chiller III the mixture is withdrawn through line 23 by means of pump 24 and recirculated through coil 25 and thence discharged through valved line 26 into chiller II. mixture is passed successively through each chiller.

The chilled mixture leaving the last chiller waxed oil flows through line 31 into storage or to apparatus for further treatment (not shown).

The last three chillers I3, I3 and I5 are chilled by means of a cooling medium such as brine. The cooling. medium is contained in a supply tank 38 from which it is withdrawn through line 39 by pump 30 and forced through line 4| into coil.

62 in chiller l5, thence through line 43 into coil M in chiller I I, and thence through line 45 into sufliciently cooled is discharged through line 3- coil 43 in chiller I3. From coil'46 the cooling medium is returned to supply tank 33 through In a similar manner, the

line H. The quantity of cooling medium supplied to each coil in chillers It, It and II may be regulated by means of valved by-pass lines It, It and In the operation of the process it will be understood that any convenient number of chillers may be used and that each chiller may be substantially of the same type as the ones illustrated in the drawings. The solution of oil and solvent may be chilled by any suitable means such as'by indirect cooling with brine, the chilled dewaxed oil produced by the process or any other cold medium. The several chillers are'maintained at diilerent temperatures by regulating by means of suitable valves the amount of refrigerating medium supplied to the chillers.

It has been found that by this method of operation larger particles of petrolatum are formed and the subsequent separatlonof the petrolatum from solution in the centrifuges is more emcient, thus allowing greater yields of dewaxed oil to be obtained. It should be understood. that this invention is not limited to the particular method and apparatus described for purposes of illustration but may be adapted to other methods of chilling in which a gradual cooling-of the oil-solvent mixture is necessary.

We claim:

1. In a process for dewaxing oils in which a mixture of oil and solvent is passed successively through a scrim of chillers each maintained at a lower temperature than the preceding one, the improvement which comprises passing the oilsolvent mixture from apreceding chiller-through a coil immersed in the liquid in the next succeeding chiller. whereby the oil-solvent mixture is indirectly cooled by the cooler liquid and thereafter introducing the oil-solvent mixture directly into the body of liquid in the cooler chiller.

2. In a process for dewaxing oils in which a mixture of oil and solvent is passed successively through a series of chillers the improvement which comprises causing the oil-solvent mixture 10 the body of cooler liquid in the said succeeding l5 chiller.

- 3. Process according to claim 1, in which the oil-solvent mixture from a preceding chiller is recycled through the coil immersed in the liquid of the succeeding chiller until it has been cooled to a temperature within a few degreesoi' that of the liquid in the said succeeding chiller.

4. Process according to claim 1, in which a portion of the ofl-solvent mixture from a preceding chiller which has been passed through the coil immersed in the cooler liquid of the next succeeding chiller is thereafter introduced directly into the body of liquid in the said succeeding chiller. and the remainder of this oil-solvent mixture is recycled through the coil; in admixture with another portion of oil-solvent mixture from the preceding chiller.

WILBIAM A. EBERLE.

LOUIS H. ZEPFLER. 

